This invention relates to bleaching activators for use in detergent compositions, and more particularly to an improved process for the preparation of bleaching activators in granular form.
It is known that so called bleaching agents are among important components of the detergent compositions.
Usually, the bleaching agents are peroxides, and a typical peroxide used in detergent compositions is sodium perborate.
However, bleaching with peroxides is practical only within a certain temperature range (80.degree.-85.degree. C.) since at lower temperatures, as would be desirable from the standpoint of avoiding discoloration of the textiles washed, and the integrity of the fibres, as well as from the point of view of saving energy, the action of peroxides is too slow.
In order to make it possible to use the bleaching agents at lower temperatures, in the range of from 40.degree. to 60.degree. C., so called bleaching activators are added to the peroxide-containing detergent compositions.
The most used bleaching activators are the acetylation products of polyalcohols or polyamines, such as for instance, penta-acetylglucose (PAC), or tetra-acetylethylenediamine (TAED).
After completion of the acetylation reaction, the final products obtained, such as penta-acetylglucose or tetra-acetylethylenediamine are poured in water, in order to free them from the undesired reaction by-products, which are soluble in water. In this manner an aqueous suspension of PAC or TAED (which are water insoluble) is obtained which, after filtration, gives rise to a cake containing from about 30 to 65% water, depending on the filtration process used.
In the known technique, the thus obtained cake must be subjected to drying, and the dry activator powder must be coated with suitable protective compounds, before adding it to a detergent composition. The above entails many problems, among which the following are cited:
(a) The acetylated products are, as is well known, thermolabile compounds, with low m.p. so that they are degraded or also easily melted at the drying temperatures.
(b) During the granulation step, it is necessary to add a suitable binder, in order to secure the mechanical strength.
(c) During the granulation step it is necessary to again introduce water, which must be again eliminated in a subsequent drying operation.
All the above operations, besides affecting the cost of the final product and the length of the process, induce, due to the repeated thermal treatment operations, a more or less great degradation of same, which is particularly evidenced by the coloring of the product.